Abbas Al-Hawasi M.B.Ch.B. M.D. Departement of ophthalmology and experimental medicine

Linköping University

Sweden

Nordic Pediatric Ophthalmology Group and Nordic Strabismus Association meeting, Åland 2015.

Eye tracker.

Video-oculography (VOG) is a non-invasive, video-

based method of measuring horizontal, vertical and torsional position components of the movements of both eyes (eye tracking) using a head-mounted mask that is equipped with small cameras.(Wikipedia).

Video oculography

Video oculography

Trans Am ophthalmolo Soc. 1987;85:320-31.

Pictures with permission from BcnInnova.

Gazelab ®

Patient management interface

9 Gaze positions test

Tracking

Nystagmus analysis

Objectives: To compare the strabismus measurement done by Gazelab® to measurement done by orthoptists.

Methods: o 2 experienced orthoptists how had no expeireince of Gazelab.

o An instructer how showed the orthoptists who to use the device.

o Patients (n=9) had been examined by orthoptist with prism cover test in 9 PG.

o 1 person without strabismus been examind as a reference.

o Different causes of strabismus, with/out previous strabismus operations.

o 8 male and 1 female. 20-77 years old with mean age 53.3 years.

o Same orthoptist used the Gazelab to examine the patient either with 9GP (n=6) / tracking program (n=9).

o The both uncovered, cover right and cover left results was of our interest for horizontal and vertical deviations. The primary strabismus measurement was chosen.

o Standard pupil size measurement and medium device sensitivity.

Gazelab® VS orthoptists:

Variation was ignored

9 GP: • Total points (n=72).

• Overall 70.8 % was within 5 PD and 94.5 % was within 10 PD.

• 82.22% within 5 PD and 97.7 % within 10 PD for vertical measurements.

• 75 % within 5 PD In primary positions.

• Mean difference and median was 4 PD.

• Confidence interval was 0,066 - 1,779.

Tracking: • Total points (n=65).

• Overall 83 % was within 5 PD and 93.84 % was within 10 PD.

• Only one reading in PP was not within 5 PD ( 88.88%)

• Mean difference was 3,5 PD and median 2 PD.

• Confidence interval was 0,866 - 3.06.

Results:

The device measures within 17° at 3 meters while the

orthoptist supposed to measure within 25° at 5 meters.

We noticed that with changing the distance to 3 meters we could get more accurate and comparable results.

The first 2 patients were with more errors compared to later.

Duration of examination reduced from 40 minutes with the first patient to about 6 minutes in compare to the last one.

Worth to note:

Between 70-90 % accuracy in compare to experienced orthoptist*.

Some points measured with Gazelab could be accepted even if they were not like orthoptists measurement because it was more comitant deviations which may raise the accuracy even more.

More standard than manual PCT.

Easy and fast when the user become familiar with the device.

Added information by graphic analysis with video record of different movements.

Ability for saccadic test, pupillography and nystagmus measurements.

The Gazelab that we used has a good potential in measuring strabismus and even for more improvements.

More studies are needed to make this method more accurate and practical.

If we could make a comparison we can compare the VOG to Humphry perimetry and the orthoptist measurement to Goldman perimetry.

We think the automated measurements like VOG is the future of strabismus measurements.

Discussion

*Which one was really more accurate, the Gazelab or the orthoptist?

A question to be answered

Thank You

Åland yesterday

Åland yesterday

Åland yesterday